HF Digital Communications -...

HF Digital Communications

How to work those strange

sounds you hear on the air

John Clements KC9ON Stephen H. Smith WA8LMFJoe Miller KJ8O John Mathieson AC8JWBrian Johnston W8TFI 1 May 2014

Contents

� Introductions

� Why Digital?

� Digital Modes of Operation

� Hardware : Radio, Computer, and interfaces

Contents

� Software

� Tips and Tricks

� Q&A

Introductions

� John Clements KC9ON� Licensed in 1979 at age 16

� Retired from electronics manufacturing and IT systems

� Active experimenter and home brewer

� jwc123@gmail.com

Introductions

� Stephen Smith WA8LMF

� Land-Mobile-Radio Systems & Field Engineer

� Ham since 1964

� WA8LMF@wa8lmf.net

Introductions

� Joe Miller KJ8O

� SWL since 1967, first licensed in 2006 and collects QSL cards

� President of OCARS (W8TNO)

� Certified Public Accountant

� kj8o.ham@gmail.com

Introductions

� Brian Johnston W8TFI� Licensed in 1976

� Computer operator for a major newspaper

� Avid experimenter and home brewer

� w8tfi@arrl.net

Introductions

� John Mathieson AC8JW

� Licensed since about 2005

� Active in CW and digital modes

� jspokes@yahoo.com

Why Digital?

� Send and receive text, images, data, and audio

� Some modes work very well in noisy and weak signal environments� If you can’t hear them you can’t work them is no longer true!

Why Digital?

� Some modes can provide error free or reduced error transmissions.

� Good for Emergency Communications

Why Digital?

� Many modes use smaller bandwidths than voice

� 97.1(b) contribute to the advancement of the radio art.

� 97.313(a) use the minimum transmitter power necessary to carry out the desired communications.

Digital Modes of Operation

� There are more digital modes than you can shake a stick at!� RTTY, PSK, QPSK, MFSK, Olivia, MT63, JT65, Contestia, Hellschreiber, Throb, Packet, WSPR, SSTV, FreeDV and many many more!

Digital Modes of Operation

� Each have their own good and bad

� We will just look at a few popular ones……

The Old Timers of DigitalCW

� CW is the oldest digital mode

� Started before the birth of radio

� Computers are not required

� From QRSs in seconds per ‘dit’

� To QRQ speeds greater than 150WPM

The Old Timers of DigitalRTTY (Radio Teletype)

� Became popular in the 1950’s using WWII surplus equipment.

� 60WPM / 45 baud (changes per second)

� FSK - Shifts between 2 frequencies, typically 170Hz apart.

� Sensitive to QSB and QRN, no error correction.

PSK31

� One of the first sound card modes� Popular for keyboard to keyboard� Narrow 31Hz bandwidth� 5 conversations fit in the same

space as RTTY� 30% slower than RTTY

� 40WPM / 31 baud� Sensitive to QSB and QRN, No error

correction but outperforms RTTY

MFSK16

� Like RTTY but uses 16 different frequency shifts

� Old technology mode - required complicated hardware before sound card software was available

� Speed of 78WPM / 62.5 baud with a 316 Hz bandwidth

� ARRL Bulletins are transmitted in MFSK16

MFSK16

� Uses forward error correction (FEC)� Typically this is done by sending

redundant data� The cost penalty is extra time to

send the data multiple times� Result is greatly reduced errors

from QSB, QRN and Multipath propagation

MT63

� MFSK Variation using 64 frequency shifts

� Great for sending large amounts of data

� Forward error correction, can lose up to 25% and still have perfect copy

MT63

� 3 Modes of operation� MT63-500 50WPM 500Hz BW� MT63-1000 100WPM 1KHz BW� MT63-2000 200WPM 2KHz BW

� Typically MT63-2000 is used by EMCOMM and MARS

Olivia

� Another MFSK Variant

� Has forward error correction like MT63

� Good with QSB, QRM

� Will decode 10-14dB below the noise floor

Olivia

� Common bandwidth, shifts, and speeds

Mode BW Shifts WPM

500/16 500 16 20

1000/32 1000 32 24

JT65/JT9

� QRPp & EME Weak signal mode� JT65 uses 65 shifts in a 355Hz

bandwidth� JT9 – Fairly new mode

� Uses 9 shifts in only 15.6Hz bandwidth

� Sounds like a constant tone

JT65/JT9

� Very slow mode!� 45 seconds long to send 72 bits or ~13 characters

� Standard messages typically contains two call signs, a grid locator or signal report, the message type.

JT65/JT9

� Now also used on HF

� W6CQZ wrote “JT65-HF”that makes HF operation easy, especially for low power stations.

� http://sourceforge.net/projects/jt65-hf/files

JT65/JT9

� Actual off-the-air RX in central MI with mobile whip on 20 meters.

SSTV� Started with dedicated hardware using surplus

long-persistence RADAR CRT’s; now all done with sound-card software.

� Commonly called a “digital” mode, but most SSTV is analog, except for “EasyPal” which is actually a general-purpose digital-file-transfer-over-radio program.

� Various formats of SSTV exist but most software automatically detects and handles formatting

SSTV

� Weather Fax (WeFax) is a similar mode, not used in amateur radio but can be found on the SW bands.

Digital Voice

� The future of radio??

� About ½ the bandwidth� 1.25KHz wide using a 16QPSK signal

� FM-quality noiseless voice on HF!

� Most activity on 14.236MHz

� Free software at:http://freedv.org

Digital Voice

� Requires 2 sound cards

� One for radio-to-speaker (RX)

� One for mic-to-radio (TX)

� USB sound cards are cheap

� From $1.80 to $25

Hardware

� Only 3 components needed� Radio� Computer� Audio / PTT Interface

� Optionally a Computer Aided Tuning (CAT) interface� Not required but nice to have if the radio supports it

Hardware

� How much does it cost?� Assuming you have the radio and computer…….

� Build your own interface from free to $25

� Buy commercial interfaces from $60-300

HardwareRadio

� Almost any USB HF Transceiver� Older mechanical analog VFO rigs

may NOT be stable enough for narrow modes like PSK31 but work well on modes like RTTY and SSTV.

� Newer radios with stable frequency synthesizers are best.

� Some high end rigs have PSK and RTTY built in!

HardwareComputer

� Big and fast not required� Most “XP” computers work fine!� Minimum Requirements

� Available USB or RS-232 port� Sound Card� 1GHz CPU, 100MB free RAM� 300MB Drive space� Depends on software - YMMV

InterfacesReceive

� Start today with a simple attenuator cable

� Parts are about $10 at Radio Shack, cheaper elsewhere!

� wa8lmf.net/miscinfo/Universal-Sound-Card-Cable.pdf

InterfacesReceive

InterfacesTransmitting

� Transmitting is a little more complex

� PTT keying

� Isolate the audio to prevent ground loop issues

InterfacesCommercial

� Several Manufacturers� MFJ� West Mountain (Rig Blaster)� TigerTronics

� Some models include cables� Other models require

purchasing cables for your rig

InterfacesCommercial

� Better models include a sound card built in

� Your internal PC sound card is available for regular use

� Prices from $60 - $300

InterfacesCommercial

� Older models only handle the TX side� These models use a straight RX cable and the PC LINE-IN instead of the MIC jack!

� An RX attenuator cable is still required to go into the PC Micjack

InterfacesHomebrew

� As basic as two 600-600 ohm audio transformers, a few resistors, and a $1.00 opto-isolator chip for PTT keying.

InterfacesHomebrew

Computer Audio In

Radio ReceiveAudio Out

InterfacesHomebrew

Computer Audio In

Radio Spkr/AuxAudio Out

Computer Speaker/Line Audio Out

Radio Mic/Aux Audio In

InterfacesHomebrew

Computer Audio In

Radio Spkr/AuxAudio Out

Computer Speaker/Line Audio Out

Radio Mic/Aux Audio In

Serial Port RTS Pin Radio PTT

Line

1

2

3 4

5

6

InterfacesTypical Setup

SoftwareHam Radio Deluxe

� Ham Radio Deluxe includes a program called Digital Master 780 (DM780)

� Current Commercial version 6 $100

� Older version 5 is free!

� Handles most modes including SSTV

SoftwareHam Radio Deluxe

� Also contains:� Integrated radio (CAT) control� Log book� Satellite Tracking� PSK31 super sweeper� Remote Control� And more…..

SoftwareHam Radio Deluxe

SoftwareFLDigi

� FLDigi is FREE!

� Handles most modes including SSTV and WeFax

� Also contains a log book and radio control

SoftwareFLDigi

� The program of choice for EMCOMM

� Handles radiogram and ICS forms

� Note: additional software needed for these on the FLDigi site.

SoftwareFLDigi

SoftwareOthers

� Special modes such as JT65/JT9 and digital voice require their own software

� Many other software program exists – both free and commercial

SoftwareOthers

� MultiPSK, Digipan, MixW, mmSSTV, and WinPSK are a few

� Most choices are personal preference

Comparison of modes found in DM780 versus FLDigi

PSK both Olivia both

QPSK both * RTTY both

PSKR FLDigi * RTTYM DM780 *

Contestia both Thor both *

CW both Throb both *

DominoEX both * WEFAX FLDigi

Hellschreiber both Navtex FLDigi

MFSK both SITOR FLDigi

MT63 both WWV FLDigi

Tips and TricksPower

� Reduce your power!� Unlike SSB, these modes either run at

100% duty cycle, or use multiple tones sensitive to intermodulation distortion!

� Be kind to your finals! � Keep peak power out well below key-

down CW maximum to minimize distortion.� Keep ALC to zero

� Turn off speech processing or compression

Tips and TricksJacks

� Use the Auxiliary, Accessory, “Data”, or “Packet” jacks on the radio.� Most radios from the major manufacturers have one or more of these jacks on the rear panel

� May have constant audio input, output, and PTT lines

Tips and TricksJacks

� Typical Jacks6-pin Mini-DIN 13-Pin Full-size DIN

Tips and TricksJacks

� No need to adjust the volume or mic gain all the time

� No need to unplug the speaker to hear the radio

� No need to swap the mic in and out

�You may need a mic switch!

Tips and TricksJacks

� Some radios have an audio out line in the microphone jack. This can help reduce extra cables.

Tips and TricksRSID

� Use Reed-Solomon Identification

� Short code at the

beginning of a transmission which identifies the mode

� Several programs automatically detect this and pop up a box

Tips and TricksSound Device

� Check your sound card settings in the control panel!� Turn off special effects

� Turn off pass-thru or “Listen to this device” modes

� Set rate to 16 bit 48000Hz

Tips and TricksSound Device

� Use the mixer to adjust your transmit audio using a dummy load and short 5-10 second intervals

Tips and TricksWaterfalls

RTTY-45 PSK31 MFSK16 JT9

JT65 Digital Voice

Tips and TricksWaterfalls

MT63

Olivia

SSTV

Tips and TricksFrequencies

� Common PSK31 frequencies

1.828 10.140 21.070

3.580 14.070 24.920

7.035 18.100 28.120

� Other modes are usually a few KHz from this area

Tips and TricksFrequencies

� SSTV 14.230 is popular

� Digital Voice 14.236

� MI Digital Traffic Net (MIDTN)

� 3.583Mhz Olivia 8/500

� Tu, Th, & Sa 8PM local

� http://www.midtn.ws/

Tips and TricksReferences

� ARRL www.arrl.org/hf-digital

� Ham Radio Deluxe – Free V5

� www.amateurlogic.tv/MISC/HRD/HRD_Archives.htm

� FLDigi

� www.w1hkj.com/Fldigi.html

Tips and TricksReferences

� JT65/JT9 hflink.com/jt65/� www.physics.princeton.edu/pulsar/K1JT/wsjtx.html

� FreeDV (Digital Voice)� www.freedv.org

� Olivia www.oliviamode.com

Tips and TricksReferences

Commercial Sites� Software:

� Ham Radio Deluxe V6 www.hrdsoftwarellc.com

� Interfaces� MFJ www.mfjenterprises.com� RigBlaster www.westmountainradio.com� SignalLink www.tigertronics.com

Getting started on FLDigi

Home: http://www.w1hkj.com/

Downloads: http://www.w1hkj.com/download.html

Beginners’ guide: http://www.w1hkj.com/beginners.html

Questions?

…

� This presentation and other notes can be found here:

� http://kc9on.com/ham-radio/hf-digital-modes/

� http://WA8LMF.net/miscinfo